|
For me. the real transformer challenge is associating the physical parameters (dimensions, numbers of turns, core material, and such) into model parameters. One might reasonably assert that this is no different than, say, transistors. There is a big difference, though; I can build a transformer but I am not likely to build a transistor. I do not have the capability to measure transistors sufficiently to create models, so must rely on third-parties to do that. What third party do I use for that ferrite toroid transformer that i just built?
Perhaps the solution to this is a transformer model generator (like VDMOS tool). I can handle program writing but I do not know enough about magnetics to even think about something like that. To be useful, such a model generator should rely on measurements the most of us could do in a modestly equipped lab (say, with a signal generator and an oscilloscope).?
Jim Wagner Oregon Research Electronics
toggle quoted message
Show quoted text
Susan wrote, "My big issue/stumbling-block when using 'spice simulators is transformer models; they all seem to be described in intractable terms making it difficult to translate something I have in my hand to an accurate simulation model."
That sounds like a topic for a separate subject (not this one).? The simplest transformer models are very simple.? It's the more complicated ones that can be challenging.
Andy
|
We are not supposed to discuss
design, but what is it that you find intractable?
Electrically, there are only resistance, capacitance and
inductance, but inductance leads to considering magnetic
theory. That can be troublesome due to unfamiliarity,? but it
is not really very difficult.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 17:33, Susan Parker
wrote:
toggle quoted message
Show quoted text
Sound exciting.
Very much beyond my capabilities to write something like that.
I am a hardware person, plus low level firmware for
microcontrollers.
My big issue/stumbling-block when using 'spice simulators is
transformer models; they all seem to be described in intractable
terms making it difficult to translate something I have in my
hand to an accurate simulation model.
This is both for power-supplies and for wideband audio
transformers.
Thanks.
|
Many types of transformer do
not need complicated models like Gummel-Poon for transistors,
but of course complicated models like Chan can give more
accurate results (often more accurate than is necessary, but
that also apples to transistor models, which do not account
for variations between samples). Simple models can use easily
measured or calculated parameters, so it is easy to relate the
model to the hardware.
Please note the new Subject
line.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 18:02, Jim Wagner wrote:
toggle quoted message
Show quoted text
For me. the real transformer challenge is associating the physical
parameters (dimensions, numbers of turns, core material, and such)
into model parameters. One might reasonably assert that this is no
different than, say, transistors. There is a big difference,
though; I can build a transformer but I am not likely to build a
transistor. I do not have the capability to measure transistors
sufficiently to create models, so must rely on third-parties to do
that. What third party do I use for that ferrite toroid
transformer that i just built?
Perhaps the solution to this is a transformer model
generator (like VDMOS tool). I can handle program writing but I
do not know enough about magnetics to even think about something
like that. To be useful, such a model generator should rely on
measurements the most of us could do in a modestly equipped lab
(say, with a signal generator and an oscilloscope).?
Jim Wagner
Oregon Research Electronics
Susan wrote, "My big issue/stumbling-block
when using 'spice simulators is transformer models; they
all seem to be described in intractable terms making it
difficult to translate something I have in my hand to an
accurate simulation model."
That sounds like a topic for a separate subject (not this
one).? The simplest transformer models are very simple.?
It's the more complicated ones that can be challenging.
Andy
|
BUT, what are those “easily measured or calculated parameters”? I am a circuit designer and have no idea what they are (or how to do the measurements)!. I strongly suspect that I am not alone. How about a tutorial for the wiki?
toggle quoted message
Show quoted text
On Apr 29, 2023, at 11:06 AM, John Woodgate < jmw@...> wrote:
Many types of transformer do
not need complicated models like Gummel-Poon for transistors,
but of course complicated models like Chan can give more
accurate results (often more accurate than is necessary, but
that also apples to transistor models, which do not account
for variations between samples). Simple models can use easily
measured or calculated parameters, so it is easy to relate the
model to the hardware. Please note the new Subject
line.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 18:02, Jim Wagner wrote:
For me. the real transformer challenge is associating the physical
parameters (dimensions, numbers of turns, core material, and such)
into model parameters. One might reasonably assert that this is no
different than, say, transistors. There is a big difference,
though; I can build a transformer but I am not likely to build a
transistor. I do not have the capability to measure transistors
sufficiently to create models, so must rely on third-parties to do
that. What third party do I use for that ferrite toroid
transformer that i just built?
Perhaps the solution to this is a transformer model
generator (like VDMOS tool). I can handle program writing but I
do not know enough about magnetics to even think about something
like that. To be useful, such a model generator should rely on
measurements the most of us could do in a modestly equipped lab
(say, with a signal generator and an oscilloscope).?
Jim Wagner
Oregon Research Electronics
Susan wrote, "My big issue/stumbling-block
when using 'spice simulators is transformer models; they
all seem to be described in intractable terms making it
difficult to translate something I have in my hand to an
accurate simulation model."
That sounds like a topic for a separate subject (not this
one).? The simplest transformer models are very simple.?
It's the more complicated ones that can be challenging.
Andy
|
I will certainly consider
writing something, but at the moment I am trying to cope with
the costly consequences of a hard disc crash that has all my
technical files on it.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 19:50, Jim Wagner wrote:
toggle quoted message
Show quoted text
BUT, what are those “easily measured or calculated parameters”? I
am a circuit designer and have no idea what they are (or how to do
the measurements)!. I strongly suspect that I am not alone. How
about a tutorial for the wiki?
Jim
On Apr 29, 2023, at 11:06 AM, John Woodgate
< jmw@...>
wrote:
Many types of transformer do not need
complicated models like Gummel-Poon for
transistors, but of course complicated models like
Chan can give more accurate results (often more
accurate than is necessary, but that also apples
to transistor models, which do not account for
variations between samples). Simple models can use
easily measured or calculated parameters, so it is
easy to relate the model to the hardware.
Please note the new Subject line.
======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget. I see, and I remember. I do, and
I understand. Xunzi (340 - 245 BC)
On 2023-04-29 18:02, Jim
Wagner wrote:
For me. the real transformer challenge is associating
the physical parameters (dimensions, numbers of turns,
core material, and such) into model parameters. One
might reasonably assert that this is no different
than, say, transistors. There is a big difference,
though; I can build a transformer but I am not likely
to build a transistor. I do not have the capability to
measure transistors sufficiently to create models, so
must rely on third-parties to do that. What third
party do I use for that ferrite toroid transformer
that i just built?
Perhaps the solution to this is a
transformer model generator (like VDMOS tool). I can
handle program writing but I do not know enough
about magnetics to even think about something like
that. To be useful, such a model generator should
rely on measurements the most of us could do in a
modestly equipped lab (say, with a signal generator
and an oscilloscope).?
Jim Wagner
Oregon Research Electronics
Susan wrote, "My big
issue/stumbling-block when using 'spice
simulators is transformer models; they all
seem to be described in intractable terms
making it difficult to translate something I
have in my hand to an accurate simulation
model."
That sounds like a topic for a separate
subject (not this one).? The simplest
transformer models are very simple.? It's the
more complicated ones that can be challenging.
Andy
|
On 4/29/23 1:50 PM, Jim Wagner wrote: BUT, what are those “easily measured or calculated parameters”? I am a circuit designer and have no idea what they are (or how to do the measurements)!. I strongly suspect that I am not alone. How about a tutorial for the wiki?
The most important, usually, is turns ratio. While it isn't exactly straight forward to enter that in LTSpice, it isn't difficult: Providing detailed parameters like inductance and parasitic capacitance is harder. Important if you need it but usually not so much. -- David Schultz
|
That's the trouble. Vastly
over-simplified articles like that, while not wrong, tell you
just enough to get totally confused. For example, you set the
turns ratio right, to get 6 V out from a 120 V input, but you
set the inductance of the 120 V winding 3 to 6 orders of
magnitude too low (or too high; then then transformer works
but costs $1000 too much).
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 20:10, David Schultz
wrote:
toggle quoted message
Show quoted text
On
4/29/23 1:50 PM, Jim Wagner wrote:
BUT, what are those “easily measured or
calculated parameters”? I am a circuit designer and have no idea
what they are (or how to do the measurements)!. I strongly
suspect that I am not alone. How about a tutorial for the wiki?
The most important, usually, is turns ratio. While it isn't
exactly straight forward to enter that in LTSpice, it isn't
difficult:
Providing detailed parameters like inductance and parasitic
capacitance is harder. Important if you need it but usually not so
much.
|
On 4/29/23 2:45 PM, John Woodgate wrote: That's the trouble. Vastly over-simplified articles like that, while not wrong, tell you just enough to get totally confused. For example, you set the turns ratio right, to get 6 V out from a 120 V input, but you set the inductance of the 120 V winding 3 to 6 orders of magnitude too low (or too high; then then transformer works but costs $1000 too much).
That is a design problem rather than a simulation problem. Looking at the sheet that came with some FT114-77 toroids I acquired a decade or three ago I see a formula for calculating the number of turns given a desired inductance. Which depends on a parameter that varies quite a bit depending on the particular core used. 1270mH/1000turns for this one. The trick in designing a transformer is to make it large enough so that the core doesn't saturate. But not too much larger. -- David Schultz
|
Well, again, large enough is
right, but it's only about 5% of the story. If it's a bit
bigger than necessary, there's cost and size penalties but the
transformer will, in principle, run cooler and will be more
efficient. Opposite if it's too small — hot and inefficient.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 21:25, David Schultz
wrote:
toggle quoted message
Show quoted text
On
4/29/23 2:45 PM, John Woodgate wrote:
That's the trouble. Vastly over-simplified
articles like that, while not wrong, tell you just enough to get
totally confused. For example, you set the turns ratio right, to
get 6 V out from a 120 V input, but you set the inductance of
the 120 V winding 3 to 6 orders of magnitude too low (or too
high; then then transformer works but costs $1000 too much).
That is a design problem rather than a simulation problem.
?Looking at the sheet that came with some FT114-77 toroids I
acquired a decade or three ago I see a formula for calculating the
number of turns given a desired inductance. Which depends on a
parameter that varies quite a bit depending on the particular core
used. 1270mH/1000turns for this one.
The trick in designing a transformer is to make it large enough so
that the core doesn't saturate. But not too much larger.
|
This is a suspended thread, but
I am now able to look at the proposed tutorial The first
question is, what sort(s) of transformer? While the basic
theory is the same for all, the practical design methods vary
considerably. There is no point in writing a tutorial that
no-one is interested in.
I see the occasional query
about a power supply having a mains transformer with
inductances in the mH or less range, so there may be some
interest in mains transformers.? I also see the occasional
query about audio output transformers for tubes/valves.? I
don't think anyone would try to wind their own toroidal, so we
are talking 'E's and I's', maybe with the occasional 'T's and
U's.
I'm not going to deal with
transformers for SMPS, because they need a totally different
approach, as do RF transformers with ferrite cores or no core.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-04-29 19:50, Jim Wagner wrote:
toggle quoted message
Show quoted text
BUT, what are those “easily measured or calculated parameters”? I
am a circuit designer and have no idea what they are (or how to do
the measurements)!. I strongly suspect that I am not alone. How
about a tutorial for the wiki?
Jim
On Apr 29, 2023, at 11:06 AM, John Woodgate
< jmw@...>
wrote:
Many types of transformer do not need
complicated models like Gummel-Poon for
transistors, but of course complicated models like
Chan can give more accurate results (often more
accurate than is necessary, but that also apples
to transistor models, which do not account for
variations between samples). Simple models can use
easily measured or calculated parameters, so it is
easy to relate the model to the hardware.
Please note the new Subject line.
======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget. I see, and I remember. I do, and
I understand. Xunzi (340 - 245 BC)
On 2023-04-29 18:02, Jim
Wagner wrote:
For me. the real transformer challenge is associating
the physical parameters (dimensions, numbers of turns,
core material, and such) into model parameters. One
might reasonably assert that this is no different
than, say, transistors. There is a big difference,
though; I can build a transformer but I am not likely
to build a transistor. I do not have the capability to
measure transistors sufficiently to create models, so
must rely on third-parties to do that. What third
party do I use for that ferrite toroid transformer
that i just built?
Perhaps the solution to this is a
transformer model generator (like VDMOS tool). I can
handle program writing but I do not know enough
about magnetics to even think about something like
that. To be useful, such a model generator should
rely on measurements the most of us could do in a
modestly equipped lab (say, with a signal generator
and an oscilloscope).?
Jim Wagner
Oregon Research Electronics
Susan wrote, "My big
issue/stumbling-block when using 'spice
simulators is transformer models; they all
seem to be described in intractable terms
making it difficult to translate something I
have in my hand to an accurate simulation
model."
That sounds like a topic for a separate
subject (not this one).? The simplest
transformer models are very simple.? It's the
more complicated ones that can be challenging.
Andy
|
For those who are interested in modelling tube amplifiers and the output transformers used:?I have a thread on DIYaudio? with easy to use LTspice transformer models.
There are currently 3 flavours: Push-Pull with ultra-linear taps, Ditto with extra cathode feedback windings and Single-ended. I am working on a Hammond 125A. Just enter the numbers from the transformer datasheet. All tedious calculations are done by LTspice in the model.
Something like [Rpp=8k Lpp=1220 UL=35 Cp=390p Rp=152 RS4=0.145 K=0.9999987] for an AMPLIMO Toroidal Output Transformer type 20PP8K0S.
Comments are welcome,
Ite
|
The only issue I see with that is that it doesn't take into
account the fact taht inductance decreases as frequency increases.
The ratio is typically 4:1 between 20Hz and 20kHz.
So using the LF inductance all along results in using a too high
coupling coefficient in order to agree with the HF response.
I routinely use 2 or 3 different values of Lnom depending on
frequency.
toggle quoted message
Show quoted text
For those who are interested in modelling tube amplifiers and the
output transformers used:?I have a thread on DIYaudio? with easy
to use LTspice transformer models.
There are currently 3 flavours: Push-Pull with ultra-linear taps,
Ditto with extra cathode feedback windings and Single-ended. I am
working on a Hammond 125A. Just enter the numbers from the
transformer datasheet. All tedious calculations are done by
LTspice in the model.
Something like [Rpp=8k Lpp=1220 UL=35 Cp=390p Rp=152 RS4=0.145
K=0.9999987] for an AMPLIMO Toroidal Output Transformer type
20PP8K0S.
Comments are welcome,
Ite
|
Jerry,
What causes a transformers inductance to decrease with increasing frequency?
It sounds like my model of how audio transformers work is too simple.
? --? Gavrik
The only issue I see with that is that it doesn't take into
account the fact taht inductance decreases as frequency increases.
The ratio is typically 4:1 between 20Hz and 20kHz.
So using the LF inductance all along results in using a too high
coupling coefficient in order to agree with the HF response.
I routinely use 2 or 3 different values of Lnom depending on
frequency.
For those who are interested in modelling tube amplifiers and the
output transformers used:?I have a thread on DIYaudio? with easy
to use LTspice transformer models.
There are currently 3 flavours: Push-Pull with ultra-linear taps,
Ditto with extra cathode feedback windings and Single-ended. I am
working on a Hammond 125A. Just enter the numbers from the
transformer datasheet. All tedious calculations are done by
LTspice in the model.
Something like [Rpp=8k Lpp=1220 UL=35 Cp=390p Rp=152 RS4=0.145
K=0.9999987] for an AMPLIMO Toroidal Output Transformer type
20PP8K0S.
Comments are welcome,
Ite
|
It depends how you measure
inductance. A real inductor has series resistance (copper
loss) and parallel resistance (iron loss).? You can measure in
two ways? - as a series RL network and as a parallel RL
network.? Neither gives you the true behaviour over a large
frequency range. You can model this in LTspice to see what
happens.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
toggle quoted message
Show quoted text
Jerry,
What causes a transformers inductance to decrease with
increasing frequency?
It sounds like my model of how audio transformers work is
too simple.
? --? Gavrik
The only issue I see with that is that it doesn't take
into account the fact taht inductance decreases as
frequency increases.
The ratio is typically 4:1 between 20Hz and 20kHz.
So using the LF inductance all along results in using a
too high coupling coefficient in order to agree with the
HF response.
I routinely use 2 or 3 different values of Lnom depending
on frequency.
For those who are interested in
modelling tube amplifiers and the output transformers
used:?I have a thread on DIYaudio? with easy to use
LTspice transformer models.
There are currently 3 flavours: Push-Pull with
ultra-linear taps, Ditto with extra cathode feedback
windings and Single-ended. I am working on a Hammond 125A.
Just enter the numbers from the transformer datasheet. All
tedious calculations are done by LTspice in the model.
Something like [Rpp=8k Lpp=1220 UL=35 Cp=390p Rp=152
RS4=0.145 K=0.9999987] for an AMPLIMO Toroidal Output
Transformer type 20PP8K0S.
Comments are welcome,
Ite
|
Actually inductance also varies with level. These are the "magic"
properties of iron cores. Basically, shaking the magnetic domains
is more difficult at the start of the magnetization curve (until
it reaches saturation), and more difficult as frequency increases.
There are models for simulation of the inductance vs. level (see
Chan modle), but I'm not aware of models for simulation of
inductance vs. frequency.
Maybe someone can chime in...?
toggle quoted message
Show quoted text
Jerry,
What causes a transformers inductance to decrease with
increasing frequency?
It sounds like my model of how audio transformers work is
too simple.
? --? Gavrik
The only issue I see with that is that it doesn't take
into account the fact taht inductance decreases as
frequency increases.
The ratio is typically 4:1 between 20Hz and 20kHz.
So using the LF inductance all along results in using a
too high coupling coefficient in order to agree with the
HF response.
I routinely use 2 or 3 different values of Lnom depending
on frequency.
For those who are interested in
modelling tube amplifiers and the output transformers
used:?I have a thread on DIYaudio? with easy to use
LTspice transformer models.
There are currently 3 flavours: Push-Pull with
ultra-linear taps, Ditto with extra cathode feedback
windings and Single-ended. I am working on a Hammond 125A.
Just enter the numbers from the transformer datasheet. All
tedious calculations are done by LTspice in the model.
Something like [Rpp=8k Lpp=1220 UL=35 Cp=390p Rp=152
RS4=0.145 K=0.9999987] for an AMPLIMO Toroidal Output
Transformer type 20PP8K0S.
Comments are welcome,
Ite
|
To be clear, I am not talking
about the sort of 'design' posted by ik.weide. I mean choosing
the core size and material, and the number of turns of the
gauge of wire that will fit on the bobbin.
======================================================================================
Best wishes
John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget.
I see, and I remember.
I do, and I understand.
Xunzi (340 - 245 BC)
On 2023-07-18 15:06, John Woodgate
wrote:
toggle quoted message
Show quoted text
This is a suspended thread,
but I am now able to look at the proposed tutorial The first
question is, what sort(s) of transformer? While the basic
theory is the same for all, the practical design methods
vary considerably. There is no point in writing a tutorial
that no-one is interested in.
I see the occasional query
about a power supply having a mains transformer with
inductances in the mH or less range, so there may be some
interest in mains transformers.? I also see the occasional
query about audio output transformers for tubes/valves.? I
don't think anyone would try to wind their own toroidal, so
we are talking 'E's and I's', maybe with the occasional 'T's
and U's.
I'm not going to deal with
transformers for SMPS, because they need a totally different
approach, as do RF transformers with ferrite cores or no
core.
======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget. I see, and I remember. I do, and I
understand. Xunzi (340 - 245 BC)
On 2023-04-29 19:50, Jim Wagner
wrote:
BUT, what are those “easily measured or calculated parameters”?
I am a circuit designer and have no idea what they are (or how
to do the measurements)!. I strongly suspect that I am not
alone. How about a tutorial for the wiki?
Jim
On Apr 29, 2023, at 11:06 AM, John Woodgate
< jmw@...>
wrote:
Many types of transformer do not
need complicated models like Gummel-Poon for
transistors, but of course complicated models
like Chan can give more accurate results (often
more accurate than is necessary, but that also
apples to transistor models, which do not
account for variations between samples). Simple
models can use easily measured or calculated
parameters, so it is easy to relate the model to
the hardware.
Please note the new Subject line.
======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget. I see, and I remember. I do,
and I understand. Xunzi (340 - 245 BC)
On 2023-04-29 18:02, Jim
Wagner wrote:
For me. the real transformer challenge is
associating the physical parameters (dimensions,
numbers of turns, core material, and such) into
model parameters. One might reasonably assert that
this is no different than, say, transistors. There
is a big difference, though; I can build a
transformer but I am not likely to build a
transistor. I do not have the capability to measure
transistors sufficiently to create models, so must
rely on third-parties to do that. What third party
do I use for that ferrite toroid transformer that i
just built?
Perhaps the solution to this is a
transformer model generator (like VDMOS tool). I
can handle program writing but I do not know
enough about magnetics to even think about
something like that. To be useful, such a model
generator should rely on measurements the most of
us could do in a modestly equipped lab (say, with
a signal generator and an oscilloscope).?
Jim Wagner
Oregon Research Electronics
Susan wrote, "My big
issue/stumbling-block when using 'spice
simulators is transformer models; they all
seem to be described in intractable terms
making it difficult to translate something I
have in my hand to an accurate simulation
model."
That sounds like a topic for a separate
subject (not this one).? The simplest
transformer models are very simple.? It's
the more complicated ones that can be
challenging.
Andy
|
Jerry,
?
Thanks for your comment, I didn't know that the inductance decreases at higher frequencies.
The modification of the model to correctly reflect the decreases at higher frequencies is beyond my expertise. I leave that to someone else.
But I think my model is already a big step forward compared to using a bunch of coupled coils with odd values on the schematics.?
?
Ite
|
I would separate this in two answers:
1) if you are getting from a manufacturer a standard transformer- ask your manufacturer for supporting you with measured data about the specifications given.And the simulation model parameter.
Additional also on getting the coupling capacitance primary to secondary. As this is your pain point later on in EMI....
If they can?t support you- then you have to measure it on your own. How to do? Please see book "Trilogy of Inductors", 5th edition, section I.4.3 Transformer Parasitic parameter and equivalent circuit, pg. 121ff.
2) for a customized transformer ? Well, with same target specifcations, you will find different solutions by winding arrangement, insulation layer, core material, bobbin, etc etc.
This all has an impact on the final specfcations. And so also on the parasitics incorporated in the individual design. The best way then is to measure the sample as described above. Everything else, is guessing...
?
|
Hi.
Ltspice comes with :
-linear inductors (no saturation)
-Non linear inductors (arbitrary magnetic flux definition in the form Flux=function() ) Input Flux= in the inductance line? of the inductor. But that does not help much for accurate modelling.
-Chan model Non linear inductors (these expect Br Bs Hc parameters, Br is B flux remanence, Bs is B field saturation, and Hc is H field coercivity) These can be read from a BH curve. (relationship between magnetic field H (Amperes/m) and magnetic flux B (Tesla))
The problem is that core manufacturers do not usually publish BH curves in their datasheets nor Br Bs and Hc parameters.?
But BH curves can if, I remind well, be obtained with some PSPice tool.
Other way is to obtain a BH curve with a BH curve meter plug into an oscilloscope. If you have a core sample. There are some circuits available on how to build one or they can be bought.
Finally the Chan model needs the core geometry. (core section area and magnetic length). These can be calculated using basic toroid geometry formulas.
Ltwiki has an article about The Chan model.
This resource is also helpful :
There is also an even more accurate model : the Jiles Atherton model (very slow) named CoreJA by Mr Bordodynov. (although I did not use it personnally)
Finding Jiles Atherton parameters can be even harder. Thankfully There is a magnetic.txt file attached to the CoreJA Model with some cores parameters.
Hope you find this information helpful
|
This has been decomposing in my system while I
had all those computer problems. The situation is that I looked
to see if there are any suppliers of laminations and bobbins,
and I found that there were two, but they have both closed down,
presumably due to lack of demand. I would still write a
tutorial, but I don't see much point, if people can't use it.
On 2023-04-29 19:50, Jim Wagner wrote:
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BUT, what are those “easily measured or calculated parameters”? I
am a circuit designer and have no idea what they are (or how to do
the measurements)!. I strongly suspect that I am not alone. How
about a tutorial for the wiki?
Jim
On Apr 29, 2023, at 11:06 AM, John Woodgate
< jmw@...>
wrote:
Many types of transformer do not need
complicated models like Gummel-Poon for
transistors, but of course complicated models like
Chan can give more accurate results (often more
accurate than is necessary, but that also apples
to transistor models, which do not account for
variations between samples). Simple models can use
easily measured or calculated parameters, so it is
easy to relate the model to the hardware.
Please note the new Subject line.
======================================================================================
Best wishes John Woodgate OOO-Own Opinions Only
Rayleigh, Essex UK
I hear, and I forget. I see, and I remember. I do, and
I understand. Xunzi (340 - 245 BC)
On 2023-04-29 18:02, Jim
Wagner wrote:
For me. the real transformer challenge is associating
the physical parameters (dimensions, numbers of turns,
core material, and such) into model parameters. One
might reasonably assert that this is no different
than, say, transistors. There is a big difference,
though; I can build a transformer but I am not likely
to build a transistor. I do not have the capability to
measure transistors sufficiently to create models, so
must rely on third-parties to do that. What third
party do I use for that ferrite toroid transformer
that i just built?
Perhaps the solution to this is a
transformer model generator (like VDMOS tool). I can
handle program writing but I do not know enough
about magnetics to even think about something like
that. To be useful, such a model generator should
rely on measurements the most of us could do in a
modestly equipped lab (say, with a signal generator
and an oscilloscope).?
Jim Wagner
Oregon Research Electronics
Susan wrote, "My big
issue/stumbling-block when using 'spice
simulators is transformer models; they all
seem to be described in intractable terms
making it difficult to translate something I
have in my hand to an accurate simulation
model."
That sounds like a topic for a separate
subject (not this one).? The simplest
transformer models are very simple.? It's the
more complicated ones that can be challenging.
Andy
|
John Woodgate